Previous research in this Laboratory has examined personality profiles of cultures obtained by averaging traits assessed in samples of college students and adults. We have extended this line of research by examining ratings of 12 to 17 years old in 24 cultures. Observer ratings of adolescents were obtained using the NEO Personality Inventory-3 (NEO-PI-3), a more readable version of the Revised NEO Personality Inventory (NEO-PI-R), which showed good psychometric properties across cultures. Aggregate scores were generalizable across age and gender and showed convergence with culture-level scores from previous studies of self-reports and observer ratings of adults. Non-Western cultures tend to score slightly lower on a dimension related to Extraversion. Further, aggregate scores of adolescent ratings were unrelated to national character stereotypes, consistent with previous research that challenge the accuracy of these widely shared beliefs. The multinational study includes sytematic assessments of personality stereotypes of age groups and genders as well as nations. Ongoing analyses are examining whether age and sex stereotyped are shared across individuals and cultures, and whether these perceptions reflect actual age and sex differences on personality. These analyses will provide important new information on the conditions under which stereotypes are, or are not, accurate. In a further study, we examined the differential reliability and validity of facet scales from the NEO Inventories using cross-cultural, longitudinal, and family based study (N = 34,108). We evaluated the extent to which (a) psychometric properties of facet scales are generalizable across ages, cultures, and methods of measurement, and, (b) validity criteria are associated with different forms of reliability. Composite estimates of facet scale stability, heritability, and cross-observer validity were broadly generalizable. Two estimates of retest reliability were independent predictors of the three validity criteria;none of three estimates of internal consistency was. Available evidence suggests the same pattern of results for other personality inventories. Internal consistency of scales can be useful as a check on data quality but appears to be of limited utility for evaluating the potential validity of developed scales, and it should not be used as a substitute for retest reliability.